Common Defects In Rolling Stock:
Carriages and Wagons are always subjected to heavy Linear and Transverse forces, wear and tear, many types of defects can develop in the components of Rolling Stock. The following are the common defects arising in different types of Rolling Stocks.
RUNNING GEAR DEFECTS:
Wheel Defects: – Sharp flange, Thin flange, Less radius at the root of the flange, Deep flange, Hallow tire, Thin tire and Flat tire.
Axle Defects:- Bent Axle, Notched Axle, Grooved Axle, Scored journal, Warm box, Hot Axle and defective bearing. Failure of lubrication, Failure of Roller Bearing components.
SPRING GEAR DEFECTS:
Broken spring and its fittings like shackle and shackle pin broken, weak springs and shifted springs.
DRAW GEAR DEFECTS:
Drawbar, screw coupling, springs or any part of draw gear broken or worn-out beyond permissible limit and Train parting.
BUFFING GEAR DEFECTS:
Dead buffer, Drooping buffer, any component of buffer broken or damaged beyond limits, low buffer height due to overloading, uneven loading, weak spring or any other cause.
BRAKE GEAR DEFECTS:
Inoperative brake cylinder, defective brake system, defective brake rigging and failure of brake gear components, Brake binding.
BODY AND OTHER DEFECTS:
- Corrosion to the body panels, floor, roof, side and end body panels, etc.
- Defective door and its locking arrangements
- Roof panels leaking non-water tightness
- Defective or damaged safety/amenity fittings.
The Hot axle is a very serious axle defect. The unnoticed hot axle can cause journal cut and leading to a major derailment.
- Metallic Creech or whistling sound
- Burning smell
- Smoke out of the axle box
- Grease or oil splashing over wheel surface
- Flameout of axle box
- Discoloring of axle box cover
- Wheels not rotating
The wheel plays a vital role in any transport vehicle. In general, the wheel is of the cylindrical section, while rolling over a flat surface covers a longitudinal distance.
All Railway wheels are having a definite wheel profile, having two main portions. The wheel profile in which the wheel tread having the conical section rolls over the Rail table with point contact which transmits the vertical load. The gauge face of the Rail guides the flanges of the wheel profile while rolling over Rail follows the path of the Rail; negotiate curve, points, and crossing etc.
The flange is subjected to lateral force. Two independent wheels are fitted over an Axle with the interference fit thereby both wheels always rotate together as a pair. Earlier the wheel will have its discover which the tire (Made out of steel) is fitted with the shrunk fit, which is called tyred wheel, later solid wheels make the wheel as a piece.
Both Rail, as well as the Wheel, is made out of hardened steel with the fine surface finish, thereby the efficiency of the transport over the Rail is high. Each wheel shares the load of the vehicle and rolls over the Rail. Normally to control the speed of any vehicle or to stop the vehicle we are applying a force (Brake force) over the wheel tread, which restricts the rotation of the wheel thereby we get retardation.
There should be some proportionate application of the brake force over the wheel with respect to its load, which is constant while on run.At the time of applying the brake force to a rotating wheel, if the force applied is more than the proportional load carried by the wheel, the rotation of the wheel is suddenly stopped, but due to momentum the vehicle still moves with its wheel in locked condition (I,e) the wheel will slide over the Rail table and travel for some distance till its momentum vanishes.
This often happens to road vehicles also when sudden brake application takes place. In another situation, the brake force is applied to the wheel when it is in stable condition and the vehicle is pulled without releasing the brakes causes the wheel to slide over the Rail without rotation.
This causes damage to the perfect roundness of the wheel tread profile with some FLAT places in its periphery is called as FLAT TYRE (FLAT TREAD). Both Rail and Wheel being the hard metals rubbing with each other, the rubbing action takes place over the length of the Rail table but for the wheel, the rubbing is at one particular contact point and hence the damage to the wheel is more.
Due to that the point contact at the spot will become an area with its length, breadth, and depth.(Generally, the breadth is the width of the Rail table and length and depth to any linear limit)
The wheel with the flat tyre, when allowed to roll over Rail, causes severe damages to the track as well as the Rolling stock and directly infringing the safe working condition. The flat spot on the wheel periphery will come in to contact the rail table on every rotation of the wheel, which gives an unusual sound and a heavy vertical shock load to the vehicle. This will damage the Roller bearing components, springs, Axle and Wheel etc in the rolling stock.
Normally the wheel in one rotation will cover about three meters (about 10 feet) so within one Km it makes about 330 hits over the Rail table. A pair of wheel with its maximum axle load ranging from 13 to 22.3 tonnes with the flat tyre will make a severe hit over the Rail table at every 3 meters. In the welded Rail sections every 13-meter length of the rail we have got a welded Rail joint which is the weakest section of the Rail.
If the flat place on the wheel hits over a welded joint it causes heavy shock load there by the crack developed at the joint and leading to rail crack and weld failure that is highly dangerous and unsafe situation.In several major accident cases the flat tyre wheel of a train, which will not make the dangerous situation immediately.
In due course of time, the internal crack developed to the extent of the total failure of the rail leading to a major disaster in which it is not possible to find out the culprit or to fix the correct response for the failure because of time lag.
Hence the flat tyre wheel should not be allowed to roll over the rail and to be detected in time. Keeping the seriousness of flat tyre in mind a joint safety circular No.T.157/XV/83/Vol.II dated 10.06.2004 issued by the HQrs, in which it is clearly stated the symptoms, the responsibility of each category of staff in detecting this defect.
MECHANICAL C&W STAFF & EMU/MENU MAINTENANCE STAFF:
As per Railway Boards guidelines, the permissible flat tyre on wheel tread is limited to 60mm for Goods and 50mm for the coaching stock/locomotives. All C&W Train Examination staff should be counseled to adhere to the provision of para “tyre defects” of part IV IRCA Conference Rules for coaching stock of part III of IRCA Conference Rules for Freight stock.
The TXR staff shall be vigilant during the rolling in an examination to look out for flat tyres and they should inspect and assess the extent of flat from OFF side of the train on arrival at platform and yard. The wheel profile is to be closely examined during under gear examination in pit line and also during the outgoing examination in the goods yard. This aspect is to be closely watched during rolling out examination also when the train is started from the station. Normally bi wagon/coach with flatness beyond the permissible limit shall be allowed online.
On detection of the flat tyre, in the locomotive/rolling stock involved has been checked and confirmed by loco shed staff/C&W staff that the flat tyre is beyond the permissible limit, in case of loco, it should be moved to the nearest loco shed having pit wheel lathe for attention and coach/wagon may be moved to the next TXR point having facility to change the wheels. If the condition of the flat tyre is so severe, arrangements may be made to change the wheels at the wayside station itself.
Speed restriction of 40KMPH should be observed until the loco/rolling stock is moved to loco shed/TXR point.
DRIVER, MOTORMAN, AND GUARD OF THE TRAIN:
The train crew and shunting staff should be trained to release brakes whenever they operate DV isolating cock. Drivers of all air brake trains after making a full-service brake application must wait for 40 seconds before restarting. For an emergency brake application, he must wait for 90 seconds before restarting.
They should be given theoretical and practical training in the working of air brake system and various time and pressure limits for effective, proper application of brake and releasing of the break in the train.The empty/load box device should be kept in the empty/loaded position depending upon the empty/loaded condition of the stock to avoid skidding of wheels resulting into flatness of tyre during the run.
The Driver and Guard should also be vigilant in the detection of hammering sounds below while on run and on detection of the same should isolate the AR and DV duly draining the air in the AR completely and release the brakes on the particular stock. They should observe a speed restriction of 40KMPH to clear the section up to next station, where they should stop the train and advise control office regarding the flat tyre and ask for C&W/Loco staff to attend.
Station staff/train passing staff should be on the lookout to detect any ‘hammering sound’ during the passage of the train. Such staffs, who by their vigilance and alertness detect such unusual sound, shall inform the SM who should immediately inform the section control and take the following action.
To advise the Driver of the train through Walkie—talkie to work his train with the restricted speed of 40KMPH until the next station, where the train should be stopped and inspected by the Driver, Guard, and SM
If any flat tyre is found, a decision shall be taken in consultation with the section controller/Carriage controller whether to detach the defective vehicle or to proceed with the restricted speed of 40KMPH until the next TXR/Loco Examination station in which case SM shall issue a caution order of 40 KMPH.
In case it is not possible to establish any communication with the Driver, the SM/ASM shall inform, the nearest Gatekeeper, to be vigilant of the approaching train and take suitable action to stop the train before it causes extensive damages. The GK shall inform the Driver of the train in which flat tyre is available, who in turn shall work his train at restricted speed to next station and take action as in (a) above.
In case both the above actions are not possible, the SM/ASM will inform to the next station to stop the train and the train should be jointly inspected by the Driver, Guard, and SM and if any flat tyre is found, further action as provided.
The section controller should note the advice of flat tyre reported by stations seriously and should not allow running of the train for an onward journey without ensuring proper examination by C&W/Loco staff. On advice, the train should be stopped at next station and should not be allowed to cause avoidable damage to track and accident
JE/SE(P.Way Engineers) during their inspections by trolley/foot should be vigilant and detect any flat tyre in the engine or rolling stock of trains on the run. Other permanent way staff such as Gang man should also be counseled similarly and aided to identify flat tyres, which can be easily detected by the hammering sound. In case any such defect is noticed, they should inform immediately the nearest SM or Engineering Control through control phone or from nearest Level Crossing Gate.
Gatekeepers, in particular, should be more vigilant and report cases of flat tyres immediately on observing the same to the SM in the direction of the movement or to the SM where he has telephone connections. If in the opinion of the Gateman the hammering sound is very severe, he may take steps for stopping the train by exhibiting Hand Danger signals.
Immediately on having got information about running a train having a flat tyre, the Engineering Controller on duty shall intimate P.Way Engineers of the section in the rear to get the visual inspection carried out for any damage to the rail/weld due to the hammering action of the flat-tired wheel.
If there is any reason to believe (from the observation of the track) that the flat tyre might have caused extensive damage requiring regulation of traffic, SE/P.The way shall advise the SM duty to take action to stop the train services.
In case no communication exists between onboard staff and train crew, they must without fail intimate the Guard/Driver the position of coach with the flat tyre at the next stopping station and in case of abnormal sound, he shall stop the train by pulling ACC. Further action will be taken by Driver and Guard and SM as provided.
Circumstances in which flat tyre happen in Rolling stock:
- Brake power more than the required level-wrong setting of Load/Empty box, sudden application of the brake.
- Brake not released before starting/Restarting, Traction change, and attaching, detaching including handbrake.
- Defective brake system in Rolling stock leading to brake binding.
- Wheel/Axle locked due to the failure of Roller bearing etc.
SYMPTOMS OF WHEEL SLIDING OVER THE RAIL WHEN VIEWED FROM SIDES:
- Wheel when sliding over rail will have metallic rubbing sound emitting spark and smoke between wheel and Rail table.
- Rail table will have a continuous scratch mark.
- Will also give a rattling noise and heavy draft force in the drawgear and coupling, heavy thrust on the brake gear components.
Symptoms of wheel sliding over the rails:
- When there is brake binding in the formation, wheel not rotating and sliding over the Rail will give a jerky movement in its linear axis and with some unusual sound in the coach.
- This can be felt by experience and keen watching of the movements on run.
- In locomotive the jerk will be felt and also the hauling will be poor, section speed could not be maintained, over current drawn by the traction motors etc.